Refactor read_dist()

[kelly-sovacool]

Resolves #13

Checklist

(~Strikethrough~ any points that are not applicable.)

• ~[ ] Write unit tests for any new functionality.~
• ~[ ] Update roxygen comments & vignettes if there are any API changes.~
• ~[ ] Update NEWS.md if this includes any user-facing changes.
• [ ] The check workflow succeeds on your most recent commit.